Curious nail pigmentation

Nail pathology

Dr. Emmanuelle Bourrat

Saint-Louis Hospital

The clinical case
Now it's your turn!
Co-prescription and advice

Clinical case presentation

This young woman was in remission from severe systemic lupus diagnosed a few months earlier with cutaneous, articular, neurological and renal involvement.

She was receiving intensive immunosuppressive therapy, including an initial single infusion of an anti-CD20 agent (obinutuzumab), systemic corticosteroid therapy which was being very gradually withdrawn, mycophenolate mofetil and hydroxychloroquine (200 mg/day for a weight of 43 kg).

She was surprised by the unusual discoloration of all her nails, which were not affected by the initial skin involvement. A band of melanonychia a few millimeters high, transverse to the base of the nails at lunula level, was noted. The rest of the dermatological examination was unremarkable, with no cutaneous or mucosal hyperpigmentation. No contact factors (nail polish, artificial nails, etc.) were found on examination.

Your turn

What is your diagnosis?

Select 1 answer(s) from the following choices:

Specific onychia in cutaneous lupus

Ethnic melanonychia

Addison’s disease

Hydroxychloroquine-related iatrogenic chromonychia

Wrong answer!

Good answer!

Selected diagnosis

In our patient, the most likely cause of this pigmentation is hydroxychloroquine-induced chromonychia. Nail pigmentation not directly related to melanocytic proliferation may be longitudinal, transverse or diffuse and may have multiple causes:

Toxic: especially heavy metals (silver, copper, thallium)
Iatrogenic: synthetic antimalarials, chemotherapy (bleomycin, minocycline, amiodarone, etc.)
Exogenous (nail hardeners)
Endocrine (Addison's disease)
Metabolic (Wilson’s disease, hemochromatosis, pellagra)
Functional: microtrauma, especially on dark phototypes.

The appearance of these melanonychias is rarely specific to a particular etiology and it is the context that is more likely to point to the cause, as well as the curvature of the melanonychia when it is transverse:
- Convex (parallel to the lunula): suggestive of an internal cause
- Concave (parallel to the posterior fold): suggestive of an external cause.

Explanation of wrong answers

Nail involvement in lupus is rare, and causes pseudo-lichenoid dystrophies rather than dyschromia.

Ethnic melanonychia is very common in dark phototypes, is longitudinal and often polydactylous.

Hyperpigmentation induced by the adrenal insufficiency of Addison’s disease also affects the nails in the form of fairly diffuse longitudinal melanonychias associated with highly suggestive hyperpigmentation of the backs of the hands and palmar creases.

Message from the expert

Synthetic antimalarials are a not uncommon cause of skin and nail pigmentation, which can occur as early as the first few months of treatment. It is a relatively benign side effect but one that can worry patients, who should therefore be warned.

References

^{Bahloul E, Jallouli M, Garbaa S, et al.}^{Hydroxychloroquine-induced hyperpigmentation in systemic diseases: prevalence, clinical features and risk factors: a cross-sectional study of 41 cases.}^{Lupus. 2017;26(12):1304-1308.}